The present invention relates to a semiconductor device having an electrode pad and a method of manufacturing the same.
Products with giga-Hz operating frequencies are popular along with micropatterning and high-speed operations of semiconductor devices. A technique for high-speed operation uses a flip-chip structure using a copper electrode pad. As shown in FIG. 7, in this flip-chip structure, a silicon oxide cover layer 1102 and a polyimide protective film 1103 are formed on an uppermost interconnection layer 1101 of a semiconductor integrated circuit chip. A through hole is formed to extend from the protective film 1103 to the interconnection layer 1101. A copper electrode pad 1104 is formed to be connected to the interconnection layer 1101 through the through hole.
In this structure, however, since the end portion of the electrode pad 1104 rides on the end portion of the opening of the protective film 1103 with poor adhesion properties. The electrode pad 1104 is readily peeled from the protective film 1103. In this structure, the electrode pad 1104 is held with a bonding force of the interconnection layer 1101. When the semiconductor integrated circuit is further micropatterned, and the interconnection layer 1101 is further thinned, the bonding area decreases. As a result, the peeling problem becomes more conspicuous.
As opposed to the above structure, a structure with an electrode pad shown in FIG. 8 is available (Japanese Patent Laid-Open No. 2004-071906). In this semiconductor device, after a copper electrode pad 1203 is formed, the upper central portion of the electrode pad 1203 is exposed. A polyimide protective film 1204 is formed to surround the electrode pad 1203. In the structure part of which is illustrated in FIG. 8, peeling of the electrode pad 1203 can be suppressed. After a silicon oxide cover layer 1202 is formed on an uppermost interconnection layer 1201 of the semiconductor integrated circuit chip, a through hole is formed in the cover layer 1202 to reach the interconnection layer 1201, and the electrode pad 1202 is connected to the interconnection layer 1201 via the through hole.
In the general manufacture of semiconductor devices, it is difficult to etch copper by dry etching using a reaction gas or the like. The copper electrode pad is formed as follows. A copper film is formed by plating or the like, a mask pattern is formed by the photolithography technique, and the copper film is selectively removed by wet etching using an etching solution (chemical solution) and the mask pattern as a mask.
When the electrode pad 1203 is formed by wet etching as described above, a copper residue by wet etching is left on the cover layer 1202 around the electrode pad 1203. The copper residue forms an electrical path (leakage path) connected to the electrode pad 1203. Leakage occurs in the electrode pad 1203. This causes the decrease in yield and adversely affects the functions of semiconductor devices to degrade reliability. For these reasons, improvements are required.